Bearing indicating device



Dec. 16, 1947. c5 c U 2,432,778

BEARING INDICATING DEVICE Filed May 13, 1943 2 Sheets Sheet 1 F I A;

we M/PUT Dec. 16, 1947. I c, LUCK 2,432,778

BEARING INDICATING DEVICE Filed May 15, 1943 2 Sheets-Sheet 2 D i in- Cttorucg V Patented Dec. l6, 1947 2,432,778 BEARING INDICATING DEVICE David G. C. Luck, Hightstown, N. J assignor to Radio Corporation of America, a corporation of Delaware Application May 13, 1943, Serial No. 486,800 Claims. (Cl. 250-11) more particularly to the geometric composition of vectors automatically to indicate a resultant of two or more component vectors.

The problem of vector composition arises in many fields. One example is in radio direction finding systems, wherein an array of spaced antennas provide information as to the relative phases of an incoming signal at the locations of the individual antennas. This information may be made available as phase differences between low frequency currents by heterodyning the output of a local oscillator with the signals picked up by the antennas. If the directional array comprises two pairs of antennas spaced along two mutually perpendicular horizontal lines, as in the familiar Adcock arrays, these electrical phase differences are the rectangular components of a vector which is a horizontal projection of a vector lying along the direction of wave arrival. The length of this horizontal projection is a function of the frequency of the arriving wave and of the antenna spacing.

It is sufficient for the purpose of radio direction finding to obtain only the horizontal projection. This may be done by means of a cathode ray tube as described in copending U. S. application Ser. No. 432,841 filed February 28, 1942 by David G. C. Luck. In some cases, however, a mechanical arrangement is to be preferred. The phase differences can be transformed into mechanical motions by means of phase responsive servo systems and a vector composition mechanism.

It is the principal object of the present invention to provide an improved method of and means for mechanical vector composition in response to phase differences such as may be derived from a spaced antenna radio direction finder system.

This and other objects will become apparent to those skilled in the art upon consideration of the following description with reference to the accompanying drawing of which Fig. 1 is a schematic diagram of a phase responsive vector composition mechanism embodying the instant invention, Fig. 2 is a schematic circuit diagram of a phase responsive servo system, and- Figs. 3, 4 and 5 are schematic diagrams of a modified vector composition mechanism.

Referring to Fig.1 the low frequency output circuits of a direction finder system, not shown, are connected to a pair of phase detectors l and 3. It is assumed, for the sake of simplicity of explanation, that the antenna pairs lie on the north, south and east, west lines respectively. The low frequency voltage derived from the north antenna is applied indirectly to a phase detector I. The voltage from the south antenna is applied through a variable phase shifter l to the phase detector I. The voltage from the west antenna is applied directly to the phase detector 3 and the voltage from theeast antenna is applied through a variable phase shifter 5 to the phase detector 3. The output circuits of the phase detectors I and 3 are connected through amplifiers 9 and II respectively to reversible D.-C. motors l3 and 15. The shaft of the motor I3 is mechanically conected to a roller [1 and to the variable phase shifter l. The shaft of the motor I5 is similarly coupled to a roller l9 and the variable phase shifter 5. The rollers l1 and I9 are disposed at right angles to each other as indicated in Fig. l. 'A second pair of rollers 2| and 23 are arranged to cooperate with the rollers l1 and I9 respectively to support a pair of endless belts 25 and 21 for motion at right angles to each other. The length of each of the belts 25 and 2'! is an integral number of times the circumference of the supporting rollers. Each of the belts 25 and 21 carries transverse marking bars 29 of length and spacing each equal to the roller circumference. A transparent scale 3| is supported over the belts 25 and 21. The scale 3| is provided with concentric circular markings and radial lines centered over the region in which the belts cross. The belts 25 and 21 are made of opaque material. the upper belt 25 comprise transparent slots. The bars 29 on the lower belt 21 may be trans parent, or opaque and of color contrasting to that of the belt material.

The operation of the system of Fig. 1 is as follows:

The magnitudes and polarities of the outputs of the phase detectors I and 3 depend upon the relative phases of the respective pairs of inputs, as described below with reference to Fig. 2. The phase detector outputs are amplified by the amplifiers H and 9 respectively and applied to the motors l3 and I5. The motor i3 is ener gized by the amplifier 9 to drive the phase shifter I to a position such that the two inputs to the phase detector are out of phase with I each other, causing the output of the detector to decrease to zero and thus deenergize the motor 13. At this time the shaft of the phase shifter 1 and the roller l'l occupy angular positions corresponding to the difference in phase- The marking bars 29 on' between the inputs from the north and south antennas. Any change in this phase difference causes a corresponding change in the difference in phase between the two inputs to the phase detector I, which accordingly produces a D.-C. output voltage of a polarity depending upon which of the inputs leads the other in phase. This D.- 'C. output controls the amplifier .9 to energize-the'motor |3"to*run in the proper direction to reestablish the 90 relationship between the inputs to the detector I. Thus the roller I is maintained substantially continuously :in .an angular position corresponding to the difference in phase between the northsand sou'th antennas. The roller I 9 is similarly driven to *a position corresponding to the difference in phase between the voltages from the east and'the'westuantenna-s by the motor 15.

Since the marking bars on the belts 25 and 27 are spaced from each other by a distance equal to the circumferences .of the supporting rollers, one and only one :marking bar on the upper belt will .cross only-one :markin'gbar on the lower belt at any position of the :rollers 2H and i9. The point of intersection 33 .lies at such a position that ra .line .3?! drawn from the point 33 to the center -35 of ".the scale 3| will lie in -a .direction corresponding :to ithezazimuth represented i'by "the relative phases .of the .input voltages. Thus the iangularrpositi'on of theipoint 33 provides :a direct :bearing indication upon the scale 3|. .The "radial distance of the ipnint 33.from the center 35 .isfaiiunction 'Of Lthe:signal frequency, the antenna sspacingendthe elevation of the wave arrival. This distance :ma'yhe determined with reference :to the 'circularsgraduations on the scale afll and :the :information converted by .means .of nomographic "charts aor tables to determine .the -.elevation. Since only one .pair of marking bars can intersect :at .a time, the indication .is unambiguous sand .:no restraint is placed upon .free rotation of the phase shifters '5 and :1 and miotors 1'3 :and 15. If ."a phase difference goes beyond ;the normal range, "for example "when the system :is tuned from one'station, having a bearing 35f :less :than 180 to one having a bearing-of more than 21.809, another mark 29 on the corresponding belt comes into action.

Numerous: modifications of "the-device: arapossible. For example, :the .upper :belt may be opaque, white, and marked by transparent slits, while the under-beltiis opaque, wl1ite,and:marked by black lines, 'giving an indication "as :a ;black dot marking the :ti iii the vector :resultant of the two inputs. .Theuppenbelt may .bGtlEtIlS- parentwith marks like' those of the under -:belt providing a crossed lineiindication. Both belts maybe transparent, .marked with opaque .lines and moved over a background which beaI'Sxlihe scaleand may, if desired,:be luminous. .-A; further possibility lies in the use: of two opaquebelts with transparent slits and a luminous background. providing :a bright dot indication.

Referring :to Fig. 2,.thephase detectors :l :and. 3 each comprise :a pair .of :diodes 7H and 1-3 "connected symmetrically with an input transformer Hi-and output resistors 71. --One .ofth'e variable phase directional input :voltages is-applied across the transformer primary. The :phase shifters 5 and .1 each comprise a phase :splitting network including resistors 19 and 119' and-capacitors 8.! and 8!. This network :is conne'cted to a :voltage divider--83 comprising a resistor :85 and 'a.;p'air of -.angular1y,:mov.able contact 1 arms M and 89.

'to-the phase splitting network at the points 93 .andr93'. The resistors 19 and 19' and the capacitors BI and 8| are related to each other so that the voltage betweenthe points 9| and 9| is out "of phase with 'the voltage applied to the points 93 and93. The variable sliders 81 and 8.9'ane'connected-to the midpoints of the input and output resistors 71 and 15 respectively. The slidersill and 89 are mechanically connected together, as indicated by the dash line 95, and are coupled to a .common controlashaft, not shown.

.The ;oper.a'.tion.of;the-;system of Fig. '2 :isas'follows:

One directional input'voltage is.applied to the anodesrof thediodes SH and 11.3 in opposite, polarities. The .other input :voltage is applied .to .the anodesofthe diodes s'kl and :13 zthrough thexphase shifter in :the same polarity. LWhen the two .input voltages are :in :phase .at .the :diode :1 I, they are -:out of .phase at the :diode .causing the diode 'H '.to.:conduct .during altern-ate zhalf .rcycles while-the. diode 1.3 does-not conduct. Thiscauses current to rflow throughizhe upper half of 'the output :resistor E'I'Lso .th'atithe upper :end of the output resistor .is positive with :respect to the lower end. When :the directional input .voltages arerout of, haseizatsthediode :I l they are int-phase at the diode 3, causing conduction through the diode 7 3 and current through the lower -half of the resistor :11. This causes the'lowenenddf the resistor 17 to :become positive with -respect to the upper en'd. The magnitude of'the voltage across the resistor 1 1 is a 'fun'ction o'f thephase 'angle between the input voltages to the diode network.

' When the two*input-voltages-are$0-' out of phase with respect to each -'other,both diodes conduct during period of equal lengthsothat the'resultant voltage across theresistor'l'l is zero.

Figs. 3, 4 and 5 shown modified vector "composition mechanism suitable *for providing mechanical output'for the "operation of a physical pointer orthe like. Phase shifters 5' and 1', similar to the phase shifters '5 and"! ofFig. 1 but arranged to, provide 720 phase change "for one shaft rotation, are coupledmechanically as indicatedby .the dash lines 38.and {391th 'two'double spiral. cams .41 and 113 respectively. .The .cams BI and 43 areene igeYd by followers 45 and 4.1 supported on rods '49 and'5l and guided formetion radially .of the ,respective -cams floy. means .-.of bearings53. The rods .49 and 5| are, provided with slotted.crossheads.55:andfi'l, engaging a,.pin 59 at the intersection of the;slots. An armliLis supported for .pivotalmotion about an axis L63, extending through .the central. positionoi the ,pin 59. The armel .is. pr.o.vided with a slot 62sengaging the pin59. .The .angular.position .ofthe pin 59with respectto theicenterrfiiisa unique function of the angularpositions-of.thenams H and 43. The rm 5.! .is movedzby' the .pin'. 5.9.to.a-.corresponding .-angular position. .An.index--.65 may be provided-atthe end-.ofthe arm :lil for-cooperation ofzaasuitable scale :66 toprovide bearing indication, A.=scale :61 may Joe provided -nn--the .arm

6| against which an index 69 on the pin 59 may be read to indicate the elevation of angle.

Although the system of Fig. 3 has been described as applied to the purpose of indication, it is to be understood that the mechanical output of the device may be employed to operate a position plotter or any other desired mechanism.

I claim as my invention:

1. In a radio direction finder system wherein the azimuth of arrival of a radio wave is indi cated in terms of the phase of two A.-C. voltages, a pair of phase responsive servo mecha nisms each connected to respond to the difierence in phase between one of said A.-C.. voltages and a reference A.-C. voltage, two members mechanically disposed for motion at right angles to each other, one of said members being connected to each of said servo mechanisms, linear marking means provided on each of said members and extending transversely thereon at right angles to the direction of motion thereof, and means for indicating position of the intersection of said marking means.

2. In a radio direction finder system wherein the azimuth of arrival of a radio wave is indicated in terms of the phase of two A.-C. voltages, a pair of members disposed for motion at right angles to one another, slots provided in said members at right angles to the direction of motion thereof, electric motors coupled to said members, phase responsive detectors connected to control the power input to said motors, means for applying one of said A.-C. voltages to each of said detectors, means including variable phase shifters for applying a reference phase input to each of said detectors, mechanical connections from each of said motors respectively to each of said phase shifters, whereby said movable members are positioned so that'said slots cross each other at the position which represents said azimuth of arrival.

3. The invention as set forth in claim 2 including a longitudinal slot indicator bar supported for pivotal motion about the common central position of the slots in said movable members, and a pin extending through the slots in said movable members and said indicating bar.

4. The invention as set forth in claim 2 wherein said movable members comprise endless belts supported on rollers having perimeters equal to the length and spacing of said slots.

5. The invention as set forth in claim Z Wherein the mechanical connections from said motor to said movable members including double spiral cams, and said phase shifters are arranged to provide phase shifts of 720 electric degrees for each rotation of the shifts thereof.

DAVID G. C. LUCK. 

